3GPP (3rd Generation Partnership Project) is a project to study/create specifications of a mobile telephone system based on a network in which W-CDMA (Wideband-Code Division Multiple Access) and GSM (Global System for Mobile Communications) are evolved.
In 3GPP, the W-CDMA system is standardized as the third-generation cellular mobile communication system and its services are launched sequentially. In addition, HSDPA (High-Speed Downlink Packet Access) in which the communication speed is further increased is also standardized, and its services are launched.
In 3GPP, the evolution of the third-generation radio access technology (referred to as LTE (Long Term Evolution) or EUTRA (Evolved Universal Terrestrial Radio Access)); and a mobile communication system (hereinafter, referred to as LTE-A (Long Term Evolution-Advanced) or Advanced-EUTRA) that utilizes a wider system bandwidth to thereby realize faster data transmission and reception are being studied.
As a downlink communication scheme in EUTRA, an OFDMA (Orthogonal Frequency Division Multiple Access) system performing user multiplexing by using subcarriers orthogonal to each other is proposed.
In addition, in the OFDMA system, there is applied a technology such as an adaptive modulation and coding scheme (AMCS) based on adaptive radio link control (Link Adaptation) such as channel coding.
The AMCS is a scheme for switching radio transmission parameters (also referred to as AMC modes), such as an error correction scheme, coding rate of error correction, and data modulation order, in accordance with the channel quality of each mobile station apparatus, in order to efficiently perform high-speed packet data transmission.
The channel quality of each mobile station apparatus is fed back to a base station apparatus by using a CQI (Channel Quality Indicator).
FIG. 14 is a view showing a channel configuration used in conventional communication systems. This channel configuration is used in a radio communication system such as EUTRA (see Non-patent document 1). The radio communication system shown in FIG. 14 includes a base station apparatus 100 and mobile station apparatuses 200a, 200b, and 200c. R01 denotes a range in which the base station apparatus 100 is communicable, and the base station apparatus 1000 communicates with a mobile station apparatus existing in this range R01.
In EUTRA, a physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical multicast channel (PMCH), a physical control format indicator channel (PCFICH), and a physical hybrid ARQ indicator channel (PHICH) are used in a downlink on which signals are transmitted from the base station apparatus 100 to the mobile station apparatuses 200a to 200c. 
Furthermore, in EUTRA, a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a physical random access channel (PRACH) are used in an uplink on which signals are transmitted from the mobile station apparatuses 200a to 200c to the base station apparatus 100.
Downlink control information carried by the physical downlink control channel (PDCCH) is referred to as DCI (Downlink Control Information). A plurality of formats is prepared for DCI. The format of DCI is referred to as a DCI Format (downlink control information format). A plurality of DCI Formats is present, and DCI Formats are classified by uses, the number of bits, or the like. There are DCI Formats having the same number of bits or the different number of bits. The mobile station apparatus performs reception of the physical downlink shared channel (PDSCH) in accordance with a received DCI Format. The mobile station apparatus can determine the use application of the PDCCH and/or the PDSCH and/or the PUSCH (transport channel or logical channel), the DCI format, a transmission scheme of the PDSCH, or a transmission scheme of the PUSCH due to by what identifier (RNTI) the cyclic redundancy check (CRC) of DCI is scrambled. An RNTI (Radio Network Temporary Identity) is implicitly coded by the CRC of DCI included in the physical downlink control channel (PDCCH). Specifically, by computing the logical sum of CRC parity bits of 16 bits and an RNTI of 16 bits, a CRC is scrambled by the RNTI.
Specific description of downlink-related PDCCH decoding processing will be given. A mobile station apparatus set so as to decode a PDCCH having a CRC scrambled by an SI-RNTI, a P-RNTI or an RA-RNTI decodes DCI Format 1A or DCI Format 1C in the common search space. A mobile station apparatus set so as to decode a PDCCH having a CRC scrambled by a C-RNTI, or an SPS C-RNTI decodes: DCI Format 1A in the common search space; or DCI Format 1A or DCI Formats (1, 1B, 1D, 2, and 2A) in the mobile station-specific search space. A mobile station apparatus set so as to decode a PDCCH having a CRC scrambled by a Temporary C-RNTI decodes: DCI Format 1A in the common search space; or DCI Format 1A or DCI Format 1 in the mobile station-specific search space.
Specific description of uplink-related PDCCH decoding processing will be given. A mobile station apparatus set so as to decode a PDCCH having a CRC scrambled by a C-RNTI, or an SPS C-RNTI decodes: DCI Format 0 in the common search space; or DCI Format 0 in the mobile station-specific search space. A mobile station apparatus set so as to decode a PDCCH having a CRC scrambled by a C-RNTI, and set so as to receive a PDCCH Ordered RACH for downlink data arrival decodes: DCI Format 1A in the common search space; or DCI Format 1A in the mobile station-specific search space. A mobile station apparatus set so as to decode a PDCCH having a CRC scrambled by a Temporary C-RNTI decodes DCI Format 0 in the common search space. A mobile station apparatus set so as to decode a PDCCH having a CRC scrambled by a TPC-PUCCH-RNTI, or a TPC-PUSCH-RNTI decodes DCI Formats (3A and 3) in the common search space. DCI Format 3A and DCI Format 3 can arrange TPC Commands of a plurality of mobile station apparatuses in a DCI field. Therefore, DCI Format 3A and DCI Format 3 are arranged in the common search space so that the plurality of mobile station apparatuses can perform monitoring.
Basic systems of EUTRA are followed in LTE-A. Furthermore, frequency bands used in ordinary systems are continuous in LTE-A, whereas it is proposed that a plurality of continuous/discontinuous frequency bands (hereinafter, referred to as carrier components or component carriers) is compositely used and thus they are operated as one wide frequency band (wide system band) (spectrum aggregation, or carrier aggregation). That is, one system band is configured by a plurality of component carriers each having bandwidths of a part of a system band that is available frequency bands. Mobile station apparatuses for LTE or LTE-A can operate in respective component carriers. In addition, it is proposed that, in order to more flexibly use a frequency band assigned to a mobile communication system, a frequency band used in downlink communication and a frequency band used in uplink communication have different frequency bandwidths.